Prevention of corrosion in ferrous metal pipe lines carrying refined petroleum distillates



Patented June 17, 1947 PREVENTION OF CORROSION IN FERROUS METAL PEE LINES CARRYING REFINED PETROLEUM DISTILLATES Albert A. Anderson, Hobart, Ind... assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application September 15, 1943,

, Serial No. 502,541

. 9 Claims.

This invention relates to the prevention of corrosion in pipe lines employed for the transmission of hydrocarbon oils and particularly for the transmission of refined petroleum distillates such as gasoline, kerosene and naphthas. In the transmission of gasoline thru pipe lines over long distances, considerable trouble has been encountered with corrosion and various methods have been proposed for alleviating the diiiiculty. The presence of en- I per thousand barrels of gasoline down to 0.1 pound mally saturated with water at a, higher temperature. It has been proposed to add various substances to the gasoline to inhibit the corrosion but these usually have been found objectionable either because they result in contamination of the gasoline or because they alter the character of the gasoline, tor'example by changing its color, gum content, oxidation resistance, etc. Because of the peculiar nature of this corrosion problem, the usual methods of preventing corrosion have generally been found unsuccessful.

One of the objects of this invention is to provide a method for preventing corrosion in gasoline pipe lines which is effective and economical. Another object of the invention is to provide a substance which can be added to the pipe line simultaneously with the gasoline which will control corrosion and particularly reduce pitting without having any adverse efiects on the gasoline.

I have discovered that gasoline pipe line corrosion can be controlled by adding to the line very small amounts oi sodamide. It may be conveniently added in water solution and it may be injected into the line along with th gasoline, so that the solution is carried thru the Iin' by the movement of the gasoline either entrained in the gasoline or swept along the walls or th pipe. In

this way the sodamide is brought into contact with the inside surface of the pipe line at all points where corrosion may occur.-

The amount of inhibitor required is quite small and will vary over a wide range depending on thecharacter of the gasoline, the condition of the pipe line, the season, and other factors. Thus the per thousand barrels and even as' low as .001 pound per thousand barrels .of gasoline passing thru the line. The amount required is less where thewater content is low, for example, less than 0.1 pound per thousand barrels is needed with a gasoline having less than 0.1% of water.

Instead of using sodamide I may also use a strong inorganic'base and ammonia, for example, I may use an equimolecular mixture of sodium hydroxide or potassium hydroxide with ammonia. However, a greater amount of ammonia than the equimolecular amount may be used. My experimental work indicates that less than an equimolecular amount, 1. e. less than approximately 30% of NHatp NaOH (by weight), is less eifective.

In the treatment of a pipe line carrying a stream of gasoline I may introduce the inhibitor at any one point or'at a number of points in the line.

Thus it is often possible to obtain better corrosion control by introducingsmall amounts of the inhibitor at a number of points in the line, for example points forty miles apart, rather than to introduce a large amount of inhibitor at the beginning of the line. In any case it will probably be necessary to reinhibit the stock in transit at those points where the drawofi of water is made, especially if the gasoline is permitted to settle in storage tanks under conditions in which the stock takes up moisture. When using ammonia-caustic alkali, additional ammonia and/or alkali may be added separately at different points in the line when test specimens of iron representative of the metal in the line indicate that better corrosion control throughout the length of the line is obamount required in a line already rather badly -the line. The phenomenon of iron corrosion in gasline pipe lines is a peculiar one and one which is not very well understood. The severe pitting appears to be due to the formation of islands in the line which are in contact with the gasoline but out of contact with the al ueous phase. Since the usual attempts to control corrosion depend on altering the character of the aqueous phase,

it is possible that the so-called islands are left ,unaii'ected and corrosion proceeds there unabout 5.0% to. 100% of the amount of sodamide.

hereinabove referred to.

Numerous suitable wetting agents are commercially available under various trade-names, examples being the diallwl esters of sulfo siiccinic acid, the sulfuric acid esters of the higher fatty alcohols, and the alkyl benzene sulfonates. In

general, I may employ as wetting agents watersoluble organic substances possessing to a high degree the property of reducing the surface tension of the aqueous phase while in contact with gasoline. The salts of the sulfonic acids and the organic sulfates are very effective. These substances are referred to herein as salts of organic sulfo acids. Sodium lauryl sulfate, sodium dioctyl sulfo succinate, sodium myricyl sulfate, sulfonated castor oil, sulfonated products obtained from sulfuric acid refining of viscous hydrocarbon oils and sulfon'ated olefin polymers are good wetting agents for my process. The laurol sulfates which are commercial forms of lauryl sulfates may also beemployed. An excellent wetting agent for the purpose is prepared from propylene or butylene by the following general meth- In the foregoing I have discussed particularly the corrosion in pipe lines carrying gasoline but it should be understood that the invention is also applicable to lines carrying other hydrocarbon distillates and refined petroleum products. The term gasoline pipeline" is used herein to include pipe lines carrying other refined petroleum products where the same corrosion phenomenon is present. Likewise where the term alkali amide" is employed in the claims of this application, it is intended to include sodium amide and potassium amide and the amides of any metal which forms a strong base. The term alkali amide is also employed to include stoichiometrical mixtures of ammonia and strong bases as hereinabove described.

Although I have described my invention with respect to certain applications thereof, I do not intend that it be limited except as defined in the following claims.

I claim:

1. The method of controlling the internal corrosion of a ferrous metal pipe line conducting a 0d: An olefin, for example butylene, is polymerized with aluminum chloride in the liquid phase to produce a polymer having a boiling range of about 300 to 650 F. This polymer is employed to alkylate benzene with aluminum chloride as a catalyst at about 70 to 100 F. The resulting allmlation product can be selectively sulfonated as described in U. S. patent application Serial No. 488,702, filed May 27, 1943, describing the selective sulfonation of allnvl aromatic compounds and separation of the product to produce wetting agents, employing concentrated sulfuric acid (96%). The water-soluble soap is separated and isolated as the sodium salt and employed in this form as the desired wetting agent for my pipe line corrosion inhibitor.

As an example of the effect of my inhibitor in controlling pipe line corrosion, samples of carbon steel specimens were carefully weighed and placed in a tube thru which was circulated gasoline containing a small amount (2.4%) of distilled water without any corrosion inhibitor. After forty hours four steel specimens were removed and'weighed to determine the basic corrosion rate without inhibitor. Sodium hydroxide-ammonia- Aerosol was then added equivalent in the amount of about 1.8 pounds of sodamide per thousand barrels of gasoline. The hydrogen ion concentration of the water phase is indicated by the pH of 9 to 10. The test was then continued for additional periods after which test specimens were removed and weighed with the following results:

Inches per yr. Base rate during 40 hrs. (without inhibitor) 0.0210 Corrosion rate during 384 hours (with inhibitor) -a 0.00271 refined petroleum distillate containing dissolved water, said corrosion resulting from the combined action of said distillate and a water phase separated therefrom within said line, said method comprising introducing into the stream of distillate flowing thru said line an aqueous solution of an alkali amide in which the amount of amide is not more than about 5 pounds per thousand barrels of distillate.

2. The method of claim 1 wherein said alkali amide is sodamide.

3. The method of controlling corrosion in a ferrous metal pipe line carrying a stream of refined petroleum distillate containing dissolved and separated'water, which comprises introducing into said distillate stream a'small amount of an alkali amide in aqueous solution in which the amount of said alkali amide is equivalent to about .001 to.0.5 pound per thousand barrels of distillate in said stream.

4. The method of inhibiting corrosion by distillate and separated water in a ferrous metal pipe line carrying a stream of refined petroleum distillate which comprises introducing into said petroleum distillate flowing in said line and the amount of wetting agent being about 5 to per cent of the amount of said amide.

5. The method'of claim 4 wherein said wetting agent is dioctyl sodium sulfo succinate.

6. The method of controlling corrosion by gasoline and separated water in gasoline pipe lines of ferrous metal which comprises introducing into the line while gasoline is flowing therethrough, a sufiicient amount of caustic soda and ammonia in aqueous solution to provide therein an amount of an equimolecular mixture equivalent to the hydrolysis products of sodamide within the range of 0.001 pounds and 5.0 pounds per thousand barrels of gasoline flowing in said line, the 1 amount of e. corrosion inhibiting agent, not exseeding; 5 pounds per thousand barrels of refined petroleum distillate flowing. in said. line, said agent comprising one part of an alkaline corrosion inhibitor consisting essentially of alkali mete-1 hydroxide and ammonie, the amount of said ammonia being equal to at least 30% of the combined weight of hydroxide and ammonia and about $5 to one part of a wetting agent, said 002'- rosion inhibiting agent being added to the petroieum distillate stream as an aqueous solution.

8. The method of claim 7 wherein said wetting agent is a, water-soluble salt oi an organic sulfa acicl.

9. The method of controlling corrosion by refined petroleum distillate and separated water in e ferrous metal pipe line which comprises introducing into the line, while a. stream of said distillate is flowing therethrough, an aqueous solution of a. mixture consisting essentially of alkali metal hydroxide and ammonia containing at least about 30 per cent of ammonia, based on the combined weight of the ammonia and alkali metal hydroxide, said weight of alkali metal hydroxide and ammonia, not exceeding pounds per thousend barrels of distillate in seld stream.

mm A. ANDERSON.

The following references are of record in the REFERENCES CITED I 5 file of this patent:

V UNITED STATES PAJENTS Number Number V OTHER REFERENGES Modern Inorganic Chemistry-Mellor (1988?),

page 570. 

